The disclosure of Japanese Patent Application No. 2000-236222 filed on Aug. 3, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a control apparatus and a control method for a power train including a plurality of driving power sources for transmitting power to a wheel.
2. Description of Related Art
Conventionally, a hybrid vehicle that are provided with different types of driving power sources, e.g., an engine and an electric motor is known. In this hybrid vehicle, by controlling driving/stopping of the engine and electric motor based on a running state of the vehicle, reduction in exhaust emissions, improvement in fuel economy, noise reduction and the like can be accomplished. Japanese Laid-Open Patent Publication No. 10-196427 describes an example of a driving controller of a hybrid vehicle provided with an engine and an electric motor on-board.
The hybrid vehicle described in the aforementioned publication has an engine and a motor generator as driving power sources. A first clutch is provided in a power transmission path from the engine to a transmission, and a second clutch is provided in a power transmission path from the motor generator to the transmission. A battery is connected to the motor generator through an inverter. When both the engine and motor generator operate normally, engagement/disengagement of the first and second clutches are controlled based on a predetermined normal control mode, and the vehicle runs with the power of at least either the engine or motor generator.
If at least either the engine or motor generator fails, a failure control mode different from the normal control mode is selected. More specifically, whether or not the engine is operating normally is determined based on the fuel injection amount, throttle valve opening, engine speed and the like, and the control mode is switched between the normal and failure control modes accordingly. For example, if it is determined that the engine is not operating normally, and the failure control mode is selected, the first clutch is disengaged so that the power transmission path from the engine to the transmission is cut off, while the second clutch is engaged so that the vehicle runs with the motor generator as a driving power source. This control is recognized to provide suppression of fluctuation in driving torque resulting from the failure in the engine.
The aforementioned publication describes the control in response to a failure of the driving power sources, i.e., at least either the engine or motor generator, but does not recognize the control in response to a failure in a power transmission apparatus, e.g., clutch, transmission, provided in a power transmission path from the driving power source to a wheel. Therefore, when such failure occurs, running performance of the vehicle is degraded.
It is an object of the invention to provide a control apparatus and a control method of a power train, which are capable of corresponding to a failure in a power transmission apparatus provided in a power transmission path from one of driving power sources to a wheel.
In a first aspect of the invention, a control apparatus of a power train includes a first driving power source and a second driving power source for transmitting power to a wheel, and a power transmission apparatus for transmitting the power of the first driving power source to the wheel. The control apparatus further includes a driving power controller for controlling the power transmitted to the wheel by the second driving power source when the power transmission apparatus fails.
According to the aforementioned aspect, the power transmitted to the wheel is controlled through the second driving power source when the power of the first driving power source can no longer be transmitted to the wheel, for example, due to a failure in which the power transmission apparatus cannot transmit power.
In addition to the aforementioned aspect, the driving power controller may function to transmit the power of the second driving power source to the wheel, and to prevent a load on the second driving power source during operations other than the transmission of power to the wheel.
Thus, the load on the second driving power source is reduced, whereby reduction in the power transmitted to the wheel as well as reduction in the energy required to drive the second driving power source can be prevented.
Moreover, in the aforementioned aspect, the power of the first driving power source may be transmitted to the wheel via a transmission and an output side of the transmission may be coupled to the second driving power source. In this aspect, the driving power controller may function to reduce the load on the second driving power source by controlling the transmission to function in a neutral state.
Thus, the load of the second driving power source can be reduced by controlling the transmission, thereby eliminating the need for a special separate mechanism for reducing the load on the second driving power source.
In addition to the aforementioned aspect, the power of the second driving power source may be transmitted to the wheel via a transmission, and the driving power controller may function to operate different gearshift controls in the transmission when the power transmission apparatus fails as compared to when the power transmission apparatus operates normally.
Thus, gearshift control in the transmission can operate differently when the power transmission apparatus fails as compared to when the power transmission apparatus operates normally. Accordingly, when the power transmitted to the wheel is controlled through the power of the second driving power source due to a failure in the power transmission apparatus, the torque output from the transmission is controlled similarly to when failure in the power transmission apparatus occurs.
In the aforementioned aspect, the driving power controller may function to set a gear ratio, when the power transmission apparatus fails, that is higher than a gear ratio used when the power transmission apparatus operates normally.
Thus, the gear ratio is likely to be set, when the power transmission apparatus fails, to a higher rate than that is set when the power transmission apparatus operates normally. Accordingly, when the power transmission apparatus fails, the driving power of the vehicle is higher as compared to when the power transmission apparatus operates normally.
In the aforementioned aspect, the driving power controller may function to improve an efficiency of the second driving power source when the power transmission apparatus operates normally and controls the gear ratio of the transmission to be higher than the efficiency of the second driving power source when the power transmission apparatus fails.
Thus, the efficiency of the second driving power source is improved through the higher gear ratio that is set when the power transmission apparatus fails as compared to when the power transmission apparatus operates normally. As a result, power consumption in driving the second driving power source is reduced.
In addition to the aforementioned aspect, the second driving power source may be driven with electric power, the power provided with a generator driven by the first driving power source, supplying generated electric power to the second driving power source, and the driving power controller may function to control electric power by the generator through the power of the first driving power source when the power transmission apparatus fails.
Thus, for example, when a failure occurs in the transmission apparatus, the electric power generated through the power of the first driving power source is supplied to the second driving power source. As a result, reduction in the electric power supplied to the second driving power source is prevented.
In the aforementioned aspect, the driving power controller may function to control the generator through the power of the first driving power source to generate electric power, when the power supplied to the second driving power source is reduced to below a prescribed value.
Thus, when the power supplied to the second driving power source is reduced to below the prescribed value, the generator generates electric power through the power of the first driving power source. As a result, there is a further reduction in electric power supplied to the second driving power source.
In addition to the aforementioned aspect, the power of the first driving power source may be transmitted to the wheel via a transmission, and the driving power controller may function to synchronize an input revolution speed of the transmission with an input revolution speed after gearshift when the power transmission apparatus fails, and thus the power transmitted to the wheel is controlled through the second driving power source.
Accordingly, when the power transmission apparatus fails, the input revolution speed of the transmission can be forcibly synchronized with the input revolution speed after gearshift.
In addition to the aforementioned first aspect, an autonomous revolution controller for controlling an autonomous revolution of the first driving power source may be further included. The driving power controller function to transmit the power of the second driving power source to the wheel, cause initial revolution of the first driving power source with the power of the second driving power source and to shift revolution of the first driving power source from the initial revolution to an autonomous revolution by the autonomous revolution controller.
Accordingly, provided that the vehicle is stopped and the power of the first driving power source is continuously transmitted due to a failure in the power transmission apparatus, the power of the second driving power source is first transmitted to the wheel, and the first driving power source is revolved by the second driving power source up to a revolution speed that allows an autonomous revolution. Thereafter, the first driving power source is revolved autonomously. As a result, the first driving power source can be started even when the power transmission apparatus is engaged.
In the present invention, different types of driving power sources can be used as the first and second driving power sources. More specifically, driving power sources generating power based on different principles can be used as the first and second driving power sources. A clutch capable of switching between various power transmission states, i.e., an engaged, disengaged and slipped state, and a transmission for controlling the ratio between the respective revolution speeds of input and output members can be used as the power transmission apparatus. A transmission capable of varying the gear ratio in a step-by-step manner, i.e., discontinuously, or a transmission capable of varying the gear ratio in a stepless manner, i.e., continuously, can be used as the transmission. A frictional clutch hydraulic clutch, or electromagnetic clutch may be used as the clutch.
Examples of transmission failures can include the following cases: the current gear ratio cannot be changed to another gear ratio; the gear ratio is set to a gear ratio different from the intended ratio; the transmission cannot be switched between a state in which the power transmission is not available, i.e., neutral state, and a state in which the power transmission is available; and/or the torque transmission capacity is controlled to an amount different from the desired amount.
Examples of the clutch failures can include the following cases: the torque transmission capacity cannot be changed; the torque transmission capacity is set to an amount different from the intended amount; the clutch cannot be switched from one of the engaged, disengaged and slipped states to another state; the clutch is controlled to a state different from the requested state, i.e., engaged, disengaged or slipped state.
In the invention, different gearshift control of the transmission can mean that the gear ratio to be set is different even if the running state of the vehicle, e.g., reference parameters for determining gearshift such as vehicle speed and accelerator opening, is the same.
In another aspect of the invention, a method for controlling a power train that includes first and second driving power sources for transmitting power to a wheel, and a power transmission apparatus for transmitting the power of the first driving power source to the wheel, includes a step of controlling through the second driving power source the power transmitted to the wheel when the power transmission apparatus fails.